To represent this in a picture, you would draw a rectangle and break it into 8 equal sized pieces.
For project AC, 4 out of those 8 pieces with be used (4/8 = 1/2).
For project BE, 2 out of the 8 pieces will be used (2/8 = 1/4).
You can label 4 of them AC and 2 of them BE.
To represent what is remaining you would write the following math equation.
1 - 1/2 - 1/4 = f
8/8 - 4/8 - 2/8 = f
2/8 = f
1/4 = f
1/4 of the original fabric remains after these two projects.